Using a Beta OS from years ago leaves you vulnerable to modern web exploits.
If you come across a file named MacOS_Sierra_10.12.6_Beta_5.dmg (usually ~4.8 GB to 5.2 GB), here is exactly what you are looking at.

Tiny Size: One square inch, easy to embed to devices.
OpenWrt: Easy to code; super stable, three years no reboot.
Low Cost: low cost, less than 1watt, unmatched performance.
Interfaces: Hardware support USB, Ethernet, SD, I2C, SPI etc.
OpenSource: Both software and hardware, totally FREE
Long Life: Keep production over 10 years, fast email support.
Using a Beta OS from years ago leaves you vulnerable to modern web exploits.
If you come across a file named MacOS_Sierra_10.12.6_Beta_5.dmg (usually ~4.8 GB to 5.2 GB), here is exactly what you are looking at.